Investigation of Levee Performance in Hurricane Katrina: The New Orleans Drainage Canals

The most populous of the four major protected areas that suffered significant flooding during Hurricane Katrina was the main Orleans East Bank (downtown) protected area. Two sets of failures and breaches admitted floodwaters to this region during hurricane Katrina: a series of failures along the Inner Harbor Navigation Channel - IHNC (as discussed in the companion paper), and three major breaches on the drainage canals at the north end of this populous area. The IHNC frontage failures all failed to scour paths consistently below sea level, so flow through these ceased fairly rapidly as the hurricane induced storm surge subsided. The three breaches on the drainage canals, on the other hand, all rapidly scoured to well below sea level. Flow through these thus continued for three days, eventually filling the basin and accounting for approximately half of the overall loss of life and a similar fraction of the overall damages in this catastrophic event. Flow in through these breaches finally equilibrated with the still slightly elevated waters of Lake Borgne on Thursday, September 1. This paper presents a summary of the results of an investigation of the performance of the levees and floodwalls along these three critical drainage canals.